Sensor device

ABSTRACT

A sensor, in particular a pressure sensor, having a housing  1 ; a housing interior  12  that contains a sensor element  9 ; electrical connecting elements  7  that are routed from the outside, through a housing part  2 , and into the housing interior  19  and have connecting segments  17 , which protrude into the housing interior on an inside  14  of the housing part  2  at respective entry points  15  and are electrically connected to the sensor element; and having a protective covering  21  that covers the connecting segments and the sensor element. To prevent air bubbles from getting into the protective covering, a sealing material  20  is applied onto the connecting segments  17 , at least in the region of the entry point  15  of the respective connecting segments  17  into the housing interior  19  and the part  13  of the inside  14  of the housing part  2  encompassing the entry point  15 , and the covering  21  is applied onto the sealing material  20  and the connecting segments  17.

PRIOR ART

The invention relates to a sensor, in particular a pressure sensor, withthe characteristics of the preamble to the independent claim 1.

A sensor of this kind is known, for example, from U.S. Pat. No.6,521,966 B1. By contrast with known sensors of a previous type, inwhich the sensor element was mounted onto a printed circuit board orhybrid and the connecting elements of the sensor were brought intocontact with the printed circuit board or hybrid, in the sensorsdisclosed by U.S. Pat. No. 6,521,966 B1, the sensor element, which canalso accommodate a chip with an integrated evaluation circuit, isinserted into a housing of the sensor without the use of a printedcircuit board or a hybrid. To this end, the sensor element can be glued,for example indirectly or directly, by means of an adhesive to theinside of a housing part, which is for example an injection-molded partmade of plastic, and then, by means of bonding wires, brought intoelectrical contact with connecting segments of the connecting elementsthat protrude into the interior of the housing. It is also possible tosolder decoupling capacitors (EMC capacitors) or similar components tothe connecting segments or to glue them to these segments by means of aconductive adhesive and then to attach them to the sensor element bymeans of bonding wire. To protect it from mechanical stress or exposureto chemicals, the sensor element equipped with the integrated evaluationcircuit is provided with a protective covering comprised of gel thatalso covers the bonding wires and the point at which the connectingelements exit from the plastic of the housing.

ADVANTAGES OF THE INVENTION

During application of the gel, care must be taken that no inclusions ofair get into the gel and also that no air bubbles form over the life ofthe sensor. During the application of the gel onto the sensor elementand connecting segments, even if care is taken that no air inclusionsare initially present in the protective covering, in the sensors knownfrom the prior art, it is not possible to prevent air from the regionbetween the connecting elements and the housing part—which air waseither encapsulated there from the beginning as a result of theinjection-molding process or penetrated into this region from theoutside along the connecting elements only after the manufacture of thesensor—from getting into the gel protective covering at the entry pointof the connecting segments into the housing interior. Particularly withpressure sensors, the air inclusions that get into the protectivecovering can expand explosively or can shoot rapidly through the gel,thus causing damage to the bonding wires. This renders the sensorunusable.

The sensor according to the present invention advantageously preventsair, which has penetrated into the region between the connectingelements and the plastic of the housing part or was already containedthere as a result of manufacturing, from being able to penetrate intothe gel protective covering. This is advantageously achieved by means ofa sealing material that is applied in the region of the entry point ofthe respective connecting segments into the housing interior and thepart of the interior of the housing part surrounding the entry point.The sealing material seals the entry point of the respective connectingsegments on the inside of the housing so that no air can get into theprotective covering.

Advantageous embodiments and modifications of the present invention arepossible by means of the steps taken in the dependent claims.

In a particularly simple manner, a sealing adhesive can be used as thesealing material and is applied onto the inside of the housing partequipped with the sensor element, in the region of the entry point ofthe respective connecting elements into the housing interior.

The sealing material can, in particular, be a hardenable sealingmaterial.

In an advantageous manner, the inside of the housing part is providedwith a recess for the sealing material that encompasses the entry pointof the respective connecting segments so that a dispensing unit canapply the sealing material, which then remains in the recess.

DRAWING

An exemplary embodiment of the present invention is shown in the drawingand will be explained in the description below. The sole FIGURE shows across section through a sensor according to the present invention, whichis embodied in the form of a pressure sensor in the example shown.

DESCRIPTION OF AN EXEMPLARY EMBODIMENT

The sole FIGURE shows a cross section through a sensor, which is apressure sensor in the example shown. The sensor has a housing 1, whichencloses a housing interior 19. The housing 1 is comprised of two parts:a first housing part 2 and a second housing part 3 that can be placedonto the first housing part 2. The second housing part 3 has a pressureconnection 4 with a pressure conduit 5 that feeds into the housinginterior 19. The first housing part 2 can be attached to the secondhousing part 3 by gluing, detent connection, welding, or other suitablemeans. Both housing parts 2, 3 are made of plastic in the exemplaryembodiment shown here. The first housing part 2 has connecting elements7 that are incorporated into the first housing part 2 in the form ofinsert parts. This can be accomplished, for example, by means of aninjection-molding process. The connecting elements 7 are routed fromoutside, through the housing part 2, and into the housing interior 19and have connecting segments 17 that protrude into the housing interior19, each at its own entry point 15, on the inside 14 of the firsthousing part 2. The outer ends 18 of the connecting elements 7 orientedaway from the connecting segments 17 are routed out of the housing part2 at the rear (not shown in the figure) and are used to produce contactbetween the sensor and external units.

The part 13 of the interior 14 encompassing the entry point 15 of therespective connecting segments 17 constitutes a recess that is delimitedon the side oriented away from the sensor element by an outer wall 12and on the side oriented toward the sensor element by an inner wall 11.Between the inner wall 11 and the outer wall 12, a sealing material 20is applied onto the part 13 of the inside of the housing part 2 so thatthe sealing material in the region of the entry point 15 covers theouter wall of the connecting segments 17 and the part 13 of the insideencompassing it. The sealing material 20 can advantageously be comprisedof a hardenable sealing material, for example a hardenable sealingadhesive that hermetically seals the entry point 15.

When in the unhardened state, the sealing adhesive should be as highlyfluid as possible in order to be able to favorably penetrate into thecapillaries. When in the hardened state, the sealing adhesive should bethermally stable, still ductile, and not brittle in order not tofracture when exposed to alternating temperatures. For example, a one ortwo-component epoxy resin adhesive could be used as the sealingadhesive. However, it is also possible to use a polyurethane glue, anacrylate glue, or another suitable adhesive.

The ends of the connecting segments 17 protruding into the interior 19project partway out of the sealing material 20 and are connected to thesensor element 9 by means of bonding wires 16. The sensor element 9 is apressure sensor chip that is mounted on a glass base 8, which is in turnglued, for example, to the inside 14 of the housing part 2. A protectivecovering 21 comprised of a gel, for example a silicone gel, is appliedonto the inside 14 of the housing 2, inside the region delimited by theouter wall 12. The gel completely covers the bonding wires 16, the innerwall 11, the sensor element 9, and the ends of the connecting segments17 protruding from the sealing material.

It is clear that the sealing material 20 keeps out air inclusions,which, without some sort of preventive measure, could get into thehousing interior 19 and protective covering 21 at the entry points 15 ofthe connecting elements 17. This advantageously prevents damage to thebonding wires 16.

1. A sensor, in particular a pressure sensor, having a housing (1); ahousing interior (12) that contains a sensor element (9); electricalconnecting elements (7) that are routed from the outside, through ahousing part (2), and into the housing interior (19) and have connectingsegments (17), which protrude into the housing interior on an inside(14) of the housing part (2) at respective entry points (15) and areelectrically connected directly or indirectly to the sensor element; andhaving a protective covering (21) that covers the connecting segmentsand the sensor element, wherein a sealing material (20) is applied ontothe connecting segments (17), at least in the region of the entry point(15) of the connecting segments (17) into the housing interior (19) andthe part (13) of the inside (14) of the housing part (2) encompassingthe entry point (15), and the covering (21) is applied onto the sealingmaterial (20) and the connecting segments (17).
 2. The sensor as recitedin claim 1, wherein the sealing material (20) is a hardenable sealingmaterial.
 3. The sensor as recited in claim 1, wherein the sealingmaterial (20) is a sealing adhesive.
 4. The sensor as recited in claim1, wherein the protective covering (21) is manufactured out of a gel, inparticular a silicone gel.
 5. The sensor as recited in claim 1, whereinthe part (13) of the inside (14) of the housing part (2) encompassingthe connecting segments (7) constitutes a recess for the sealingmaterial, which recess has an inner wall (11) on the side orientedtoward the sensor element (9) and an outer wall (12) on the sideoriented away from it.
 6. The sensor as recited in claim 5, wherein theouter wall (12) simultaneously constitutes a frame that laterallydelimits the protective covering (21).
 7. The sensor as recited in claim1, wherein the connecting segments (17) are electrically connected tothe sensor element (9) by means of bonding wires.
 8. The sensor asrecited in claim 1, wherein the protective covering (21) completelycovers the sealing material (20).
 9. The sensor as recited in claim 8,wherein the protective covering (21) completely covers the ends of theconnecting segments (17) protruding from the sealing material (20). 10.A method for manufacturing a sensor as recited in claim 1, wherein in afirst step, a sealing material (20) is applied onto the connectingsegments (17), at least in the region of the entry point (15) of therespective connecting segments (17) into the housing interior and thepart (13) of the inside (14) of the housing part (2) encompassing theentry point (15), and then in a second step, the protective covering(21) is applied onto the sealing material (20) and the connectingsegments (17).